Many processes exist for treating mined kaolin during the beneficiation process to improve the physical and chemical aspects of the resulting slurry, or slip, to improve its commercial value. Many of these remove contaminants of various types to improve the whiteness and purity of the kaolin and additionally employ the use of oxidation, leaching and magnetic separation. Such processes are detailed in U.S. Pat. No. 5,397,754.
Slurries of beneficiated kaolin calcium carbonate, titanium dioxide, talc, latex, other carbonates and mixtures thereof are used extensively in the paper, paint, rubber and plastics industries as coatings, fillers, extenders and pigments. These slurries are contaminatable (i.e. subject to contamination) by aerobic and anaerobic bacteria. Such contamination affects the color, odor and viscosity of the slurries, which negatively affect their commercial value.
Many treatments to neutralize the effects of this bacteria on kaolin slurries have been tried. The most conventional treatment is mixing a bactericide into the slurry to kill the bacteria. An example of this treatment is found in U.S. Pat. No. 5,496,398. Unfortunately, this treatment has a very limited period of effectiveness until contamination again occurs, because the bacteria are not completely destroyed and exposure to air produces recontamination by the aerobic bacteria that thrive on the available oxygen. Thus, the slurry must be re-treated if it is not quickly used. This repeated use of such chemicals increases the cost of producing and maintaining these slurries at acceptable levels of bacteriological contamination while assuring that the performance properties of the slurries are not degraded.
The limited life of such a treatment process presents a problem when contaminatable slurries are stored for long periods of time, a problem that is exacerbated by the conventional practice of storing slurries in open top tanks. Often, the treated slurries are shipped for long distances by truck, rail or ship, which produce re-contamination for the same reasons.
There is a need for a method of treating and shipping kaolin and calcium carbonate and other contaminatable slurries which eliminates bacterial contamination during storage and shipping and eliminates the necessity for repeated treatment by bactericides.